Swing Over Steering

ABSTRACT

A self-propelled construction machine includes a plurality of swing legs, each swing leg being supported from a ground surface by an associated crawler track steerably connected to an outer end of its associated swing leg. Pivotal movement of a swing leg may be accomplished by steering the associated crawler track through a non-zero steering angle until the lateral movement of the crawler track achieves the desired pivoting movement of the associated swing leg.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to methods and apparatus for operatingself-propelled construction machines, and more particularly, but not byway of limitation, to methods and apparatus for operating slipformpaving machines.

2. Description of the Prior Art

One known arrangement for a self-propelled construction machine includesa generally rectangular machine frame having a swing leg mounted at eachcorner of the frame and having a crawler track mounted at the free endof each swing leg. The crawler tracks provide the motive force for theconstruction machine. The mounting of the crawler tracks on the swinglegs allows the crawler tracks to be repositioned in a horizontal planerelative to the machine frame for various reasons. For example, aslipform paving machine utilizing such construction may need to spreadthe forward extending swing legs in order to make room for a paving kitor other equipment supported from the machine frame. Also, it may bedesirable during operation of the machine to relocate one or more of theswing legs and its associated crawler track to avoid obstacles. Also,the swing legs allow the crawler tracks to be repositioned for transportof the construction machine.

Various systems have been proposed for controlling the pivoting movementof the swing legs relative to the machine frame.

One system set forth in Swisher U.S. Pat. No. 3,970,405 provides thateach track is individually raised off of the ground surface one at atime, and then the swing leg is manually pivoted to the desiredorientation where it is fixed in place using turn buckles. Disadvantagesof this system include the need to individually raise each track off theground one at a time, and the need to realign the steering afteradjusting the leg orientation.

Another approach is found in Aeschlimann U.S. Pat. No. 6,872,028 inwhich the swing legs are constructed as parallelogram linkages so thatas the swing leg pivots in or out the steering direction of the crawlertrack remains unchanged.

Another solution is provided in Guntert U.S. Pat. No. 8,459,898 whichprovides a hydraulic ram between the swing leg and the machine framewhich pivots the swing leg to a desired orientation. An automaticcontroller senses the change in pivot angle of the swing leg andmaintains the steering angle of the crawler track in response to thechange in pivot angle as the swing leg pivots.

The Aeschlimann and Guntert systems offer a solution to one problempresent in the Swisher '405 patent, namely the need to individuallyraise each track off of the ground one at a time. However they create anew problem. Solutions like that of Aeschlimann or Guntert whichmaintain the steering angle of the crawler track while the swing legpivots cause a sideways skidding of the crawler track across the groundsurface. This sideways skidding contributes to wear of the crawler trackand shaking of the machine, which is undesirable especially duringpaving. These machines are quite heavy and the footprint of the tracksis large, so the resistance to this skidding action is high.

Thus there is a continuing need for improvements in the arrangements forthe control of the pivoting of swing legs of such automotiveconstruction machines.

SUMMARY OF THE INVENTION

In one embodiment a method is provided for operating a self-propelledconstruction machine, the machine including a machine frame, first andsecond swing legs pivotally connected to the machine frame, and firstand second ground engaging units steerably connected to the first andsecond swing legs, respectively. The method includes steps of:

-   -   (a) moving the machine across a ground surface under the power        of at least the first and second ground engaging units;    -   (b) as the machine moves, continuously steering the first ground        engaging unit at a non-zero steering angle relative to an        initial direction of the first ground engaging unit so that        movement of the first ground engaging unit along the ground        surface has a perpendicular component of direction perpendicular        to the initial direction and a parallel component of direction        parallel to the initial direction, and thereby pivoting the        first swing leg in a first pivotal direction from an initial        pivotal position to a revised pivotal position relative to the        machine frame as a result of the perpendicular component of        direction of the first ground engaging unit; and    -   (c) after pivoting the first swing leg to the revised pivotal        position relative to the machine frame, maintaining the revised        pivotal position of the first swing leg.

In another embodiment a construction machine includes a machine frame,first and second swing legs pivotally connected to the machine frame,and first and second ground engaging units steerably connected to theswing legs. The ground engaging units include drive motors configuredsuch that the ground engaging units are driven across a ground surfaceby the drive motors. A first steering sensor is configured to detect afirst steering angle of the first ground engaging unit relative to thefirst swing leg. A second steering sensor is configured to detect asecond steering angle of the second ground engaging unit relative to thesecond swing leg. A first lock is configured to selectively lock andunlock the first swing leg in pivotal position relative to the machineframe. A second lock is configured to selectively lock and unlock thesecond swing leg in pivotal position relative to the machine frame. Acontroller includes a swing leg pivot mode configured to allow each ofthe first and second swing legs to pivot relative to the machine framein response to steering of the ground engaging unit connected to eachswing leg while the machine moves in the direction of forward operation.

In another embodiment a method is provided of operating a self-propelledconstruction machine. The machine includes a machine frame, first andsecond swing legs pivotally connected to the machine frame, first andsecond locks configured to selectively lock the first and second swinglegs, respectively, in selected pivotal positions relative to themachine frame, and first and second ground engaging units steerablyconnected to the first and second swing legs, respectively. The methodincludes steps of:

-   -   (a) moving the machine across a ground surface under power of at        least the first and second ground engaging units, the first and        second locks being in locked positions, so that the first and        second swing legs are pivotally fixed relative to the machine;    -   (b) unlocking at least the first lock such that the first swing        leg may pivot relative to the machine frame;    -   (c) while the first lock is unlocked, moving the machine across        the ground surface and steering at least the first ground        engaging unit such that the first swing leg pivots relative to        the machine frame from an initial pivotal position to a final        pivotal position; and    -   (d) after the first swing leg reaches the final pivotal        position, locking the first lock such that the first swing leg        is maintained in the final pivotal position.

In any of the above embodiments, the second ground engaging unit may besteered simultaneously with the first ground engaging unit in adirection opposite to the first ground engaging unit.

In any of the above embodiments, the first and second pivot legs mayswing toward each other or away from each other.

In any of the above embodiments, the machine may include first andsecond linear actuators configured to hold the first and second swinglegs, respectively in selected pivotal positions relative to the machineframe. As the first pivot leg is pivoted the first linear actuator maybe de-activated so that the first linear actuator does not resist thepivotal motion of the first swing leg relative to the machine frame.

In any of the above embodiments, the linear actuators may be hydraulicrams, and the first linear actuator may be de-activated by hydraulicallyun-blocking the first hydraulic ram.

In any of the above embodiments, the first linear actuator may beactivated to hold the first swing leg in the revised pivotal position.

In any of the above embodiments, the linear actuators may activelyfacilitate the pivoting of the swing legs. This active facilitation mayresult in an absolute pivoting motion based upon an algorithm.Alternatively, this active facilitation may provide a controlledpressure to the hydraulic ram.

In any of the above embodiments, the first ground engaging unit may besteered such that the first ground engaging unit moves in a S-curvealong the ground surface beginning parallel to the initial direction,then steering away from and then back toward the initial direction.

In any of the above embodiments, the ground engaging units may besteered under control of an automatic controller in response to anoperator input corresponding to the revised pivotal position.

In any of the above embodiments, the first and second swing legs may beforward extending swing legs.

In any of the above embodiments the first and second swing legs may berearward extending swing legs.

In any of the above embodiments the construction machine may be a slipform paving machine.

In any of the above embodiments the ground engaging units may be eithercrawler tracks or wheels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a self-propelled construction machineas it moves forward from an initial position shown in the lower part ofthe figure in solid lines to a final position shown in the upper part ofthe figure in dashed lines. The left front crawler track is steered soas to pivot the left front swing leg outward as the construction machinemoves from the initial position to the final position.

FIG. 2 is a schematic plan view similar to FIG. 1 showing both the leftand right front crawler tracks being steered outward away from eachother to pivot both of the front swing legs outward away from each otheras the construction machine moves from the initial position to the finalposition.

FIG. 3 is a view similar to FIG. 1, showing the left front crawler trackhaving been steered to pivot the left front swing leg inward as themachine moves from the initial position to the final position.

FIG. 4 is a view similar to FIG. 1, showing the left rear crawler trackhaving been steered so as to pivot the left rear swing leg outward asthe machine moves from the initial position to the final position.

FIG. 5 is a schematic plan view of the left front corner of theconstruction machine of FIG. 1 illustrating the steering angle of thecrawler track relative to the swing leg, and illustrating the pivotangle of the swing leg relative to the machine frame. FIG. 5 shows thespecial case wherein swing leg initially extends straight ahead and theinitial direction of the crawler track is straight ahead.

FIG. 5A is a view similar to FIG. 5 showing the more general situationwherein the swing leg initially does not extend straight ahead and theinitial direction of the crawler track is not straight ahead.

FIG. 6 is a schematic plan view of the left front corner of theconstruction machine of FIG. 1 showing the mechanical components of thesteering system and the pivot control system of the left front swingleg.

FIG. 7 is a schematic illustration of the hydraulic power system and theelectronic control system for the steering system and the pivot controlsystem of the construction machine of FIG. 1.

FIG. 7A is a schematic illustration similar to FIG. 7 showing analternative embodiment of a hydraulic control system for blocking andunblocking the pivoting motion of the swing legs.

FIG. 7B is a schematic illustration similar to FIG. 7 showing anotheralternative embodiment of a hydraulic control system for blocking andunblocking the pivoting motion of the swing legs.

FIG. 7C is a schematic illustration similar to FIG. 7 showing anotheralternative embodiment of a hydraulic control system for blocking andunblocking the pivoting motion of the swing legs.

FIG. 8 is a schematic view of the control panel of the controller ofFIG. 7.

FIG. 9 is an enlarged view of the display screen and certain ones of theinput controls for the control panel of FIG. 8.

FIG. 10 is a schematic plan view of the construction machine of FIG. 1embodied as a slipform paving machine.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a method of operating a self-propelledconstruction machine 10. The machine 10 includes a machine frame 12. Asschematically illustrated in FIG. 10, the construction machine 10 may bea slip-form paver having a spreader apparatus 118 arranged to engage amass 120 of concrete which is shaped by form 122 so that a shaped slab124 of concrete is slip-formed by the machine 10 and exits the rear ofthe machine 10. The slip-form paving machine 10 illustrated in FIG. 10may be of any conventional construction with regard to its machine frame12 and the arrangement of supporting swing legs and crawler tracks. Themachine frame 12 may be a fixed width frame. The machine frame 12 may bea single telescoping frame which expands to one side of a main framemodule for adjustment of frame width. The machine frame 12 may be a dualtelescoping frame which extends from both sides of the main frame modulefor expansion and contraction of the width of the machine frame. Theslip-form paving machine 10 may have either three or four tracks, atleast one track being connected to an associated swing leg.

First, second, third and fourth swing legs 14A, 14B, 14C and 14D arepivotally connected to the machine frame 12 at pivotal axes 42A, 42B,42C and 42D. First, second, third and fourth crawler tracks 16A, 16B,16C and 16D are steerably connected to free ends of the swing legs 14A,14B, 14C and 14D, respectively, at steering axes 44A, 44B, 44C and 44D.The crawler tracks may be generally referred to as ground engagingunits. The ground engaging units may be crawler tracks as shown, oralternatively may be wheels.

The machine frame 12 defines a longitudinal direction 18 along alongitudinal axis 20 for forward or reverse motion of the constructionmachine 10. The machine frame further defines a lateral direction 22perpendicular to the longitudinal direction 18. The machine 10 movesacross a ground surface under the power of the crawler tracks.

As the machine 10 moves from the initial position shown in solid linesin FIG. 1 to the final position shown in dashed lines in FIG. 1, thefirst crawler track 16A is continuously steered along a path 23 andthereby pivots the first swing leg 14A. This steering and pivotingmotion is best explained with reference to FIG. 5, in which the track16A is shown in an initial orientation in solid lines, and oriented at anon-zero steering angle 24 in dashed lines. Similarly, the swing leg 14Ais shown in an initial position in solid lines, and is shown as havingbeen pivoted through a pivot angle 28 in dashed lines.

As used herein the term “continuously steered” refers to a continuousbut possibly varying steering input to the respective track throughoutthe change in track steering direction.

In the example shown in FIG. 5, for ease of illustration the initialdirection has been shown as a straight ahead direction, and the initialposition of the swing leg has been shown as a straight ahead position.But it will be understood that in the more general and typical situationthe pivot legs will not necessarily begin in the straight ahead positionand the initial steering angle of the tracks will not necessarily beginin the straight ahead direction. More generally, as shown in FIG. 5A thestarting point for a steering operation as described herein begins withthe pivot legs in an initial position and the tracks steering in aninitial direction, neither of which need be oriented straight ahead. Forexample, the forward pivot legs may already be angled away from eachother, and the tracks may be steering the machine on a curved path asseen in FIG. 5A, and from that initial starting position a steeringoperation as described below may be performed to move the pivot legseither toward or away from each other in response to steering of thetracks away from their initial steering angles.

It is noted that before the swing leg 14A can be pivoted as shown inFIG. 1, the locking mechanism associated with the swing leg must bereleased as is described below regarding the hydraulic ram or lockingmechanism 40A.

In the example of FIGS. 1 and 5, as the machine 10 moves along the path23, the crawler track 16A is continuously steered at a non-zero steeringangle 24 relative to an initial direction 19 of track 16A so thatmovement of the crawler track 16A along the ground surface has aperpendicular component of direction 26 perpendicular to the initialdirection 19, and a parallel component of direction 30 parallel to theinitial direction 19 as the track moves in the track steering direction32. Thus, assuming no slippage of the crawler track 16A, as the crawlertrack 16A moves in the track steering direction 32 by a magnitude 34,the magnitude of the perpendicular movement component 26 is indicated as36 and the magnitude of the parallel component of direction 30 isindicated as 38. It will be appreciated that as the track 16A advancesin the track steering direction 32 by one unit of magnitude, theperpendicular component 26 of movement will be equal to the sine ofangle 24, and the parallel component of movement 30 will be equal to thecosine of angle 24.

It will also be appreciated that the overall direction of the machineframe 12 is maintained in the initial direction 19 under control of theother tracks 16B, 16C and 16D which in this example will continue to bepointed straight ahead. In the more general situation as represented byFIG. 5A the machine direction may be changing as the machine 10 movesalong a curved path.

As the machine 10 moves forward from the initial position shown in solidlines in FIGS. 1 and 5, the perpendicular component of motion 26 of thetrack 16A pivots the swing arm 14A from the position shown in solidlines to the position(s) shown in dashed lines in FIGS. 1 and 5.

The movement of the swing leg 14A may be described as pivoting the swingleg 14A in a counterclockwise first pivotal direction from an initialpivot position shown in solid lines in FIG. 1 to a revised pivotalposition relative to the machine frame 12 shown in dashed lines in FIG.1, which revised position is a result of the perpendicular component ofdirection 26 of the crawler track 16A.

In the example shown in FIG. 1, the path 23 along which the crawlertrack 16A moves may be described as an S-curve along the ground surfacebeginning at a zero steering angle 24 parallel to the initial direction19, then steering at first in increasing non-zero angles as seen atintermediate positions 16A′ and 16A″ and then decreasing non-zero anglesas indicated at intermediate position 16A′″ until the first crawlertrack 16A is returned to a zero steering angle again parallel to theinitial direction in the final position indicated as 16A″″. In moregeneral terms, the S-curve may be described as beginning parallel to theinitial direction, then steering away from and then back toward theinitial direction.

It will be understood that when the machine 10 is moving along a curvedpath, as represented in FIG. 5A, the tracks will not all be steering inthe same direction. Preferably, in accordance with the Ackermannsteering principle, some or all of the tracks will be steering atdifferent angles so that each track is perpendicular to a line drawn toan imaginary common center point. In the situation of FIG. 5A, with themachine 10 moving along a curved path, the tracks associated with theswing legs which are being pivoted will not necessarily be steered backto a final direction parallel to the initial direction of the track,because the direction of the machine will have changed. Thus the trackmay be steered back to a final direction which corresponds to a currentdirection of the machine, in accordance with the desired steeringgeometry such as the Ackermann steering principle.

After the pivoting of the swing leg 14A to the revised pivotal positionrelative to the machine frame shown in the upper dashed line image inFIG. 1, the first swing leg is preferably locked in place in its revisedpivotal position. This is accomplished with a hydraulic ram 40A bestshown in FIG. 6. The hydraulic ram 40A may also be referred to as alinear actuator or as a hydraulic actuator or as a hydraulic cylinder.Also, after moving the swing leg 14A to the desired revised pivotalposition, the crawler track 16A is preferably returned to and maintainedparallel to the initial direction 19, or to another desired steeringdirection corresponding to the current direction of the machine 10.

It is noted that the linear actuators 40 could also be electricactuators rather than hydraulic actuators.

FIG. 6 schematically illustrates the mechanical components of thesteering system and the pivot control system of the machine 10.

In FIG. 6, the first swing leg 14A is shown pivotally connected to themachine frame 12 at pivotal connection or pivotal axis 42A. The firstcrawler track 16A is steerably connected to the outer end of swing leg14A so that the crawler track 16A can be steered about the verticalsteering axis 44A of a lifting column 46 by which the outer end of theswing leg 14A is supported from the crawler track 16A. As will beunderstood by those skilled in the art, extension and retraction of thelifting column 46 can raise and lower the machine frame 12 relative tothe crawler track 16A and thus relative to the ground surface. Each ofthe crawler tracks includes a drive motor 48 such that the crawlertracks are driven across the ground surface by the drive motors in aknown manner. The drive motor 48 may be either a hydraulic motor or anelectric motor.

Steering of the crawler track 16A relative to the swing leg 14A aboutthe vertical axis 44A is accomplished by extension and retraction of ahydraulic steering cylinder 50A pivotally connected at 52 to anintermediate location on the swing leg 14A and pivotally connected at 54to a steering arm 56 connected to rotate with the crawler track 16A.Alternatively, instead of the use of a hydraulic ram steering cylinder50A, the track 16A may be steered relative to the swing leg 14A by arotary actuator such as a worm gear or slew gear drive. Also, anelectric actuator may be used instead of a hydraulic actuator, to steerthe crawler track.

Each of the swing legs such as 14A may have a steering sensor 58associated therewith, which steering sensors are configured to detectthe steering angles of their respective crawler tracks relative to theirrespective swing legs. The steering sensors associated with the crawlertracks 16A and 16B are designated as 58A and 58B in the schematiccontrol diagram of FIG. 7. The steering sensors may for example each bean electro-magnetic encoder, commercially available from TWK-ElektronikGmbH, Heinrichstrasse 85,40239 Dusseldorf, Germany, as TMA 50-S A 180 WS A 16.

The swing leg 14A can be held in place pivotally relative to the frame12 by the previously mentioned hydraulic ram 40A. The hydraulic ram 40Ais pivotally connected to the machine frame 12 at pivotal connection 60and to an intermediate location on the swing leg 14A at pivotalconnection 62.

In the drawings the swing legs 14 and the hydraulic rams 40 areschematically illustrated as being directly connected to the machineframe 12. It will be understood, however, that the swing legs and thehydraulic rams do not have to be directly connected to the machine frame12. Instead, the swing legs and the hydraulic rams may be indirectlyconnected to the machine frame 12 by suitable mounting brackets. Whenone of these components is described herein as being connected to themachine frame, that includes both direct and indirect connections.

Each of the swing legs such as 14A may have a pivot sensor 64 configuredto detect the respective pivot angle 28 of the respective swing leg 14.In the schematic view of the control diagram of FIG. 7, the pivotsensors for the first and second swing legs 14A and 14B are indicated as64A and 64B. The pivot sensors may for example each be an angle sensorcommercially available from Elobau GmbH & Co. KG, Zeppelinstr. 44, 88299Leutkirch, Germany, as Part No. 424A11A05002.

FIG. 7 schematically illustrates, among other things, one embodiment ofa hydraulic control diagram for operation of the steering cylinder 50Aand the hydraulic ram 40A associated with crawler track 16A and swingleg 14A. Also shown in FIG. 7 are the similar steering cylinder 50B andhydraulic ram 40B associated with crawler track 16B and swing leg 14B.

The steering cylinder 50A and the hydraulic ram 40A may each be doubleacting hydraulic cylinders. Hydraulic fluid under pressure is providedto the cylinders from a source such as hydraulic pump 65A, and fluiddischarged from the cylinders is returned to a hydraulic reservoir 66Avia a return line 67A. Although FIG. 7 shows individual pumps 65 andreservoirs 66 for each leg, a common pump and reservoir may be used formultiple legs.

Directional control of hydraulic fluid into and out of the steeringcylinder 50A is controlled by a first solenoid actuated variable flowthree way servo-valve 68A, and control of fluid into and out of thehydraulic ram 40A is controlled by a second solenoid actuated variableflow three way servo-valve 70A.

Hydraulic fluid under pressure from pump 65A flows through a hydraulicfluid supply line 72A, to each of the variable flow three wayservo-valves 68A and 70A. These variable flow valves may also bereferred to as proportional valves. The valves 68A and 70A can controlboth the direction and the rate of flow of fluid to their respectivehydraulic cylinders.

The three way valve 70A associated with the hydraulic ram 40A has afirst position 88A wherein hydraulic fluid under pressure is provided toan upper end of the cylinder via hydraulic line 90A and received from alower end of the cylinder via hydraulic line 92A for retraction of apiston 94A of the hydraulic ram 40A. The three way valve 70A can bemoved to a second position 96A in which the direction of flow isreversed to extend the piston 94A. The three way valve 70A can be movedto a third position 98A wherein flow of hydraulic fluid to and from thehydraulic ram 40A is blocked. It is noted that the hydraulic lines 90Aand 92A may be referred to as first and second hydraulic lines 90A and92A, but such designation is for identification only and does not implyany specific functionality.

Also associated with the hydraulic ram 40A are first and second solenoidactuated bypass valves 71A and 73A connected to the hydraulic lines 92Aand 90A. Each of the bypass valves can be selectively moved to either anopen or a closed position as indicated. When in their open positions thebypass valves communicate both sides of the hydraulic ram 40A with thehydraulic reservoir 66A via the return line 67A.

Each of the hydraulic rams 40 and its associated three way valve 70 andbypass valves 71 and 73 may be referred to as a hydraulic control systemor as a lock.

The construction machine 10 includes a controller 78, which may be partof a master control system of the machine 10, or may be a separatecontroller. The controller 78 receives input signals from varioussensors such as the steering sensors 58A and 58B and the pivot sensors64A and 64B.

It will be understood that the controller 78 may receive additionalinput signals from steering sensors and pivot sensors associated withthe third and fourth tracks 16C and 16D, which additional inputs are notillustrated in FIG. 7. Controller 78 may also receive other inputs suchas advance speed or other operational parameters of machine 10.

The controller 78 can control the volume and direction of hydraulic flowto and from the steering cylinder 50A and hydraulic ram 40A via controlsignals sent to three way valves 68A and 70A, respectively, over controllines 80A and 84A. The controller 78 can control the position of thebypass valves 71A and 73A via control signals sent over control lines82A and 86A, respectively.

If three way valve 70A is in its blocked position 98A, and the bypassvalves 71A and 73A are also in their blocked or closed positions, thenthe hydraulic ram 40A is hydraulically blocked so that it cannot move.

The hydraulic control system shown in FIG. 7 associated with hydraulicram 40A has two alternative un-blocked positions.

In a first un-blocked position, if three way valve 70A is in its closedposition 98A, and the bypass valves 71A and 73A are in their openpositions, the hydraulic ram 40A is unblocked and is free to be moved byany force including but not limited to the action of the crawler track16A pivoting the swing leg 14A. This may be described as a free floatingarrangement for the hydraulic ram 40A.

In a second un-blocked position, if the three way valve 70A is in eitherof its positions 88A or 96A, and the bypass valves 71A and 73A are intheir closed positions, then the motion of the hydraulic ram 40A can beactively facilitated by hydraulic power, or can be forced by hydraulicpower, depending upon the volume of fluid supplied by pump 65A under thecontrol of controller 78.

Similarly, the three way valve 68A associated with the steering cylinder50A defines first and second positions 100A and 102A controlling thedirection of flow to and from the steering cylinder 50A, and a thirdposition 104A in which flow to and from the steering cylinder 50A isblocked so as to hold or maintain a given steering position of thecrawler track 16A relative to the swing leg 14A.

The hydraulic lines and control lines for steering cylinder 50B andhydraulic ram 40B associated with the second crawler track 16B and thesecond swing leg 14B are schematically shown on the right hand side ofFIG. 7 and analogous components are designated by the same numeralsusing a suffix B in place of a suffix A.

FIG. 7A is similar to FIG. 7 and illustrates a first alternativeembodiment of the hydraulic control systems associated with thehydraulic rams 40A and 40B. In the embodiment of FIG. 7A the three wayvalves 70A and 70B of FIG. 7 have been eliminated so that the lockingand unlocking of the hydraulic rams 40A and 40B is controlled solely bythe bypass valves. This provides what may be referred to as a freefloating arrangement of the hydraulic rams 40A and 40B. For example, theram 40A and bypass valves 71A and 73A, along with the various hydrauliclines connected thereto may be referred to as a lock or hydrauliccontrol system associated with the first swing leg 14A. That hydrauliccontrol system may be described as including the first hydraulic ram 40Ahaving a piston and a cylinder, the piston dividing the cylinder intofirst and second ends. First and second hydraulic lines 90A and 92Aconnect the fluid reservoir 66A to the first and second ends of thecylinder. The first and second bypass valves 71A and 73A are connectedto the hydraulic lines 92A and 90A, respectively. Each bypass valve hasa blocked position and a bypass position, the bypass positioncommunicating the respective end of the first hydraulic ram 40A to thefluid reservoir 66A. In the hydraulically blocked position of thehydraulic control system, the first and second bypass valves 71A and 73Aare in their blocked positions. In the hydraulically un-blocked positionof the hydraulic control system the first and second bypass valves 71Aand 73A are in their bypass positions. With this arrangement, when inthe un-blocked position, the swing leg 14A is free to be moved by theforces created by engagement of the track 16A with the ground, or withany other forces imposed on the swing leg 14A, but there is no activefacilitation of the pivoting of the swing leg by the hydraulic ram 40A.

It is noted that in the embodiment of FIG. 7A the pivot angle sensors64A and 64B are not required and may be eliminated.

FIG. 7B is similar to FIG. 7 and illustrates a second alternativeembodiment of the hydraulic control systems associated with thehydraulic rams 40A and 40B. In the embodiment of FIG. 7B the bypassvalves have been eliminated so that the locking and unlocking of thehydraulic rams 40A and 40B is controlled solely by the three way valves70A and 70B. This provides what may be referred to as a strokecontrolled arrangement of the hydraulic rams 40A and 40B. For example,the ram 40A and three way valve 70A along with the various hydrauliclines connected thereto may be referred to as a lock or hydrauliccontrol system associated with the first swing leg 14A. That hydrauliccontrol system may be described as including the first hydraulic ram 40Ahaving a piston and a cylinder, the piston dividing the cylinder intofirst and second ends. The three way valve 70A has an extension position96A, a retraction position 88A, and a blocked position 98A. Thehydraulic lines 90A and 92A connect the three way valve 70A to the firstand second ends of the cylinder. The supply line includes supply line72A and a selected one of the lines 90A and 92A, and the return lineincludes the return line 67A and the other of the lines 90A and 92A. Inthe hydraulically blocked position of the hydraulic control system thethree way valve 70A is in the blocked position 98A. In the hydraulicallyun-blocked position of the hydraulic control system, the three way valve70A is in either its extension or retraction position 96A or 88A, andthe controller 78 is configured such that the first hydraulic ram 40Aactively facilitates the pivoting of the first swing leg 14A. Thecontroller 78 may determine a specific amount of desired movement of theswing leg 14A via an algorithm, and the controller 78 may then cause aspecific volume of fluid to be delivered to hydraulic ram 40A so that astroke or extension of the hydraulic ram 40A is exactly controlled. Thealgorithm preferably calculates the exact movement of the swing leg 14Awhich will result from the steering of the track 16A, and then activelyfacilitates the movement of the swing leg by that same amount so thatfrictional forces in the swing leg assembly are compensated for by theactive facilitation. It will be understood that with this arrangement,if the algorithm is slightly in error it is the stroke imparted to thehydraulic ram 40A that will control the final pivotal position of theswing leg 14A.

FIG. 7C is similar to FIG. 7 and illustrates a third alternativeembodiment of the hydraulic control systems associated with thehydraulic rams 40A and 40B. In the embodiment of FIG. 7C the bypassvalves have been eliminated and the three way valves 70A and 70B havebeen modified to be simpler and less expensive three way valves that arenot servo-valves. Also, pressure control valves 75A and 75B have beenadded in the fluid supply lines 72A and 72B upstream of the three wayvalves 70A and 70B. With this arrangement the controller 78 isconfigured such that the active facilitation of the pivoting of theswing legs 14A and 14B by the hydraulic rams 40A and 40B is limited toproviding a hydraulic pressure to the hydraulic rams 40A and 40Bcontrolled by the pressure control valves 75A and 75B.

The arrangement of FIG. 7C provides what may be referred to as apressure controlled arrangement of the hydraulic rams 40A and 40B. Forexample, the ram 40A and three way valve 70A along with the varioushydraulic lines connected thereto may be referred to as a lock orhydraulic control system associated with the first swing leg 14A. Thathydraulic control system may be described as including the firsthydraulic ram 40A having a piston and a cylinder, the piston dividingthe cylinder into first and second ends. The three way valve 70A has anextension position 96A, a retraction position 88A, and a blockedposition 98A. Hydraulic lines 90A and 92A connect the three way valve70A to the first and second ends of the cylinder. The supply lineincludes supply line 72A and a selected one of the lines 90A and 92A,and the return line includes the return line 67A and the other of thelines 90A and 92A. In the hydraulically blocked position of thehydraulic control system the three way valve 70A is in the blockedposition 98A. In the hydraulically un-blocked position of the hydrauliccontrol system, the three way valve 70A is in either its extension orretraction position 96A or 88A, and the controller 78 is configured suchthat the first hydraulic ram 40A actively facilitates the pivoting ofthe first swing leg 14A by supplying a pressure to the selected end ofthe hydraulic ram 40A controlled by the pressure control valve 75A. Itwill be understood that with this arrangement, the steering of the track16A will control the final pivotal position of the swing leg 14A, andthe pressure provided via the three way valve 70A and pressure controlvalve 75A will merely help overcome frictional resistance to thatpivoting movement.

Controller 78 includes a processor 106, a computer readable memorymedium 108, a data base 110 and an input/output module or control panel112 having a display 114.

The term “computer-readable memory medium” as used herein may refer toany non-transitory medium 108 alone or as one of a plurality ofnon-transitory memory media 108 within which is embodied a computerprogram product 116 that includes processor-executable software,instructions or program modules which upon execution may provide data orotherwise cause a computer system to implement subject matter orotherwise operate in a specific manner as further defined herein. It mayfurther be understood that more than one type of memory media may beused in combination to conduct processor-executable software,instructions or program modules from a first memory medium upon whichthe software, instructions or program modules initially reside to aprocessor for execution.

“Memory media” as generally used herein may further include withoutlimitation transmission media and/or storage media. “Storage media” mayrefer in an equivalent manner to volatile and non-volatile, removableand non-removable media, including at least dynamic memory, applicationspecific integrated circuits (ASIC), chip memory devices, optical ormagnetic disk memory devices, flash memory devices, or any other mediumwhich may be used to stored data in a processor-accessible manner, andmay unless otherwise stated either reside on a single computing platformor be distributed across a plurality of such platforms. “Transmissionmedia” may include any tangible media effective to permitprocessor-executable software, instructions or program modules residingon the media to be read and executed by a processor, including withoutlimitation wire, cable, fiber-optic and wireless media such as is knownin the art.

The term “processor” as used herein may refer to at leastgeneral-purpose or specific-purpose processing devices and/or logic asmay be understood by one of skill in the art, including but not limitedto single- or multithreading processors, central processors, parentprocessors, graphical processors, media processors, and the like.

The controller 78 receives input data from the sensors 58 and 64. Thecontroller also receives other inputs such as the track speed andmagnitude of movement. Based upon the programming 116 the controller 78can calculate the pivot angle 28 resulting from any given steeringinputs to the tracks 16. Such calculations may be based upon thegeometry of the system shown in FIG. 5 as previously described.

As seen in FIG. 5, as the track 16A advances in the track steeringdirection 32 by one unit of magnitude, the perpendicular component 26 ofmovement will be equal to the sine of angle 24, and the parallelcomponent of movement 30 will be equal to the cosine of angle 24. Thecontroller 78 can monitor track speed and thus determine the magnitudeof movement 30 and the magnitude of the perpendicular component 26.

Knowing the magnitude of the perpendicular component 26, the change inthe pivot angle 28 can then be calculated as the angle whose sine isequal to the perpendicular component 26 divided by the distance betweenpivot points 42A and 44A.

FIG. 8 is a schematic view of the control panel 112. It will beunderstood that the control panel 112 as shown in FIG. 8 is simplifiedto show only the controls of interest, and control panel 112 willtypically include many controls other than those shown. Also, thecontrol panel 112 may comprise one consolidated control panel for allthe controls shown, or those controls may be distributed among two ormore control panels.

FIG. 9 is a schematic view of the display unit 114 of the control panel112.

The controller 78 includes a swing leg pivot mode configured to alloweach swing leg to pivot relative to the machine frame in response tosteering of the crawler track 16 associated with the swing leg 14. Theswing leg pivot mode may be selected by pressing the control button 126.The swing leg pivot mode may be implemented in either a manual sub-modeor an automatic sub-mode.

Upon initiation of the swing leg pivot mode upon pressing of button 126,the swing leg pivot mode will be in the manual sub-mode, unless theautomatic sub-mode is selected by further inputs to the control panel112.

In the manual sub-mode, the swing leg pivot mode includes a trackselection feature 128 allowing an operator to select individual steeringcontrol of either of the first and second crawler tracks 16A and 16B orsynchronous steering control of both of the first and second crawlertracks via three way switch 130, as graphically shown in FIG. 8. Afterselection of steering of the left track or right track or both, theactual steering input to either the front or rear track(s) isaccomplished ty twisting of either the forward steering control 132 orthe rear track steering control 134.

The track and leg movement corresponding to individual control solely ofthe first crawler track 16A is illustrated for example in FIG. 1. Thiswould be accomplished in the manual sub-mode by first selecting the leftposition of switch 130 and then steering with the forward steeringcontrol 132.

FIG. 2 schematically illustrates the use of synchronous steering controlof the first and second crawler tracks 16A and 16B. When using thesynchronous steering control the track selection feature is configuredto steer the first and second crawler tracks 16A and 16B in oppositedirection steering angles 24. This may be described as continuouslysteering the second crawler track 16B at a steering angle opposite tothe steering angle 24 of the first crawler track 16A and therebypivoting the second swing leg 14B relative to the machine frame 12 in asecond pivotal direction opposite the first pivotal direction of thefirst swing leg 14A.

To perform synchronous steering in the manual sub-mode, the middleposition of switch 128 is selected. In manual sub-mode, when synchronoussteering is selected, the manual steering control 132 or 134 may defaultfor example to direct steering of the left side crawler track, and thecontroller 78 will provide an equal but opposite steering input to theright side crawler track.

To perform the synchronous steering in the automatic sub-mode, commandinputs may be made to the control panel 112 through the various modeselection buttons M1-M4 and the input controls 136 as best seen in FIG.9. Inputs to the input controls 136 may quantitatively define a desiredchange in position of the swing legs by defining a desired change in thepivot angle 28, or by defining a desired change in lateral position ofthe tracks 16, or by defining a desired lateral spacing between crawlertracks or the like, or by defining any other geometrically definedparameter of the positioning of the tracks and swing legs. The processor106 may then implement algorithms contained in the program 116 to causethe tracks to steer so as to traverse a desired path such as the S-curvepreviously described, or any other curve. In performing the S-curve thetrack is steered along the ground surface beginning at a zero steeringangle 24 parallel to the initial direction 19 and then steering firstaway from and then back toward the initial direction until the crawlertrack 16 is again parallel to the initial direction or other desiredsteering direction. The other desired steering direction may for exampleby a direction of the track 16 corresponding to a current direction ofthe machine 10 which has changed during the process of pivoting theswing leg, with the appropriate direction of the track 16 beingdetermined by the Ackermann steering principle.

In the automatic sub-mode the control panel 112 may steer any selectedone of the crawler tracks to pivot its associated swing leg, or it maysteer both front tracks or both rear tracks in synchronous format aspreviously described.

In the example shown in FIG. 2, the first and second pivotal directionsare such that the first and second swing legs 14A and 14B pivot awayfrom each other. Similarly, the first and second pivotal directionscould be such that the first and second swing legs pivot toward eachother.

FIG. 3 shows an example of a laterally inward steering of the firstcrawler track 16A resulting in a laterally inward pivotal motion of thefirst swing leg 14A. The second crawler track 16B could similarly besteered laterally inward so that the second pivotal leg 14B pivotsinward toward the first swing leg 14A. The steering of FIG. 3 could beaccomplished in manual mode by first activating the swing leg pivot modevia button 126, then selecting left side steer via switch 130, thensteering with the front steering control 132. The steering of FIG. 3could also be accomplished in the automatic sub-mode via appropriateinputs to the input controls 136 and M1-M4.

As illustrated in FIG. 4, similar control may be provided to thesteering of the third and/or fourth crawler tracks 16C and 16D. In FIG.4, the situation is illustrated where the third crawler 16C has beensteered laterally outward so as to pivot the third swing leg 14C outwardas shown in FIG. 4. Both rear crawler tracks 16C and 16D may besynchronously steered either laterally outward to pivot the swing legs14C and 14D away from each other, or laterally inward to pivot the swinglegs 14C and 14D toward each other. The steering illustrated in FIG. 4may be accomplished in manual sub-mode by first activating the swing legpivot mode via button 126, the selecting left side steering via switch130, then steering via the rear steering control 134. The steering ofFIG. 4 could also be accomplished in the automatic sub-mode viaappropriate inputs to the input controls 136 and M1-M4.

During any of the steering operations schematically illustrated in FIGS.1-4, during the steering operation, when the swing legs are beingpivoted, the associated hydraulic rams 40 may be placed in an unblockedposition, which may be described as deactivating the hydraulic rams orlinear actuators, or as unlocking the hydraulic rams, so that thehydraulic rams do not resist the pivotal motion of the associated swingleg relative to the machine frame. For example, in the embodiment ofFIG. 7, hydraulic ram 40A may be placed in an unblocked position byclosing three way valve 70A and opening the bypass valves 71A and 73A.

After the steering operation is complete and the swing legs are in thedesired final position, the associated hydraulic ram 40 may be activatedby placing the hydraulic ram in a blocked position to hold or lock theassociated swing leg in the revised pivotal position. For example, inthe embodiment of FIG. 7, the hydraulic ram 40A may be placed in theblocked position by closing three way valve 70A and closing the bypassvalves 71A and 73A.

Alternatively, in the embodiment of FIG. 7, during the steeringoperation the hydraulic ram 40 may be placed in one of the activatedpositions 88 or 96 to retract or extend the piston 94 so as to activelyfacilitate the pivotal motion of the associated swing leg relative tothe machine frame. To accomplish such active facilitation of thehydraulic ram 40A, the bypass valves 71A and 73A are placed in theirclosed positions, and the three way valve 70A is moved to either itsposition 88A or 96A. The flow rate of hydraulic fluid directed to thehydraulic ram 40 may be controlled by the three way valve 70.

The hydraulic ram 40A may be described as a first hydraulic actuator 40Aconnected between the machine frame 12 and the first swing leg 14A, andconfigured to change in length as the first swing leg 14A pivotsrelative to the machine frame 12. The valves associated with the firsthydraulic actuator 40A can be switched so that the hydraulic actuator isin a hydraulically blocked position as described above preventingpivoting of the first swing leg 14A or a hydraulically unblockedposition as described above permitting pivoting of the first swing leg14A.

The controller 78 may be configured such that the hydraulic actuator orram 40 associated with each swing leg 14 to be pivoted is placed in anunblocked position prior to pivoting of the swing leg 14.

The controller 78 may be configured such that upon deactivation of theswing leg pivot mode, the valves associated with the hydraulic actuatorsor rams 40 are in their blocked positions.

Thus it is seen that the apparatus and methods of the present inventionreadily achieve the ends and advantages mentioned as well as thoseinherent therein. Although certain preferred embodiments of theinvention have been illustrated and described for purposes of thepresent disclosure, numerous changes in the arrangement and constructionof parts and steps may be made by those skilled in the art, whichchanges are encompassed within the scope and spirit of the presentinvention as defined by the appended claims.

1. A slip form paving machine, comprising: a machine frame; first andsecond swing legs pivotally connected to the machine frame; first andsecond ground engaging units steerably connected to the first and secondswing legs, respectively, the ground engaging units including drivemotors configured such that the ground engaging units are driven acrossa ground surface by the drive motors, each ground engaging unitincluding a crawler track; a first steering sensor configured to detecta first steering angle of the first ground engaging unit relative to thefirst swing leg; a second steering sensor configured to detect a secondsteering angle of the second ground engaging unit relative to the secondswing leg; a first lock configured to selectively lock and unlock thefirst swing leg in pivotal position relative to the machine frame; asecond lock configured to selectively lock and unlock the second swingleg in pivotal position relative to the machine frame; and a controllerincluding a swing leg pivot mode configured to allow each of the firstand second swing legs to pivot relative to the machine frame in responseto steering of the ground engaging unit connected to each swing leg asthe machine is driven across the ground surface by the ground engagingunits.
 2. The machine of claim 1, wherein: the swing leg pivot modeincludes a ground engaging unit selection feature allowing an operatorto select individual steering control of either of the first and secondground engaging units or synchronous steering control of both the firstand second ground engaging units.
 3. The machine of claim 2, wherein:the synchronous steering control of the ground engaging unit selectionfeature is configured to steer the first and second ground engagingunits in opposite directions.
 4. The machine of claim 1, wherein: thefirst lock includes a first hydraulic control system connected betweenthe machine frame and the first swing leg, and configured to change inlength as the first swing leg pivots relative to the machine frame, thefirst hydraulic control system having a hydraulically blocked positionpreventing pivoting of the first swing leg and a hydraulicallyun-blocked position permitting pivoting of the first swing leg; and thesecond lock includes a second hydraulic control system connected betweenthe machine frame and the second swing leg, and configured to change inlength as the second swing leg pivots relative to the machine frame, thesecond hydraulic control system having a hydraulically blocked positionpreventing pivoting of the second swing leg and a hydraulicallyun-blocked position permitting pivoting of the second swing leg.
 5. Themachine of claim 4, wherein: the swing leg pivot mode is configured suchthat the hydraulic control system associated with each swing leg to bepivoted is moved to the un-blocked position.
 6. The machine of claim 5,wherein: the swing leg pivot mode is configured such that upondeactivation of the swing leg pivot mode the hydraulic control systemsare in their blocked positions.
 7. The machine of claim 4, wherein thefirst hydraulic control system includes: a first hydraulic ram having apiston and a cylinder, the piston dividing the cylinder into first andsecond ends; a first three way valve having an extension position, aretraction position, and a blocked position; a first line and a secondline connecting the first three way valve to the first and second endsof the cylinder; and wherein in the hydraulically blocked position ofthe first hydraulic control system, the first three way valve is in itsblocked position.
 8. The machine of claim 7, wherein: the firsthydraulic control system further includes first and second bypass valvesconnected to the first and second lines, respectively, each bypass valveincluding a blocked position and a bypass position, the bypass positioncommunicating the respective line to a fluid reservoir; in thehydraulically blocked position of the first hydraulic control system,the first and second bypass valves are in their respective blockedpositions; and in a first hydraulically un-blocked position of the firsthydraulic control system, the first three way valve is in its blockedposition and the first and second bypass valves are in their bypasspositions; and in a second hydraulically un-blocked position of thefirst hydraulic control system, the first and second bypass valves arein their blocked positions and the first three way valve is in eitherits extension or retraction position, and the controller is configuredsuch that the first hydraulic ram actively facilitates the pivoting ofthe first swing leg.
 9. The machine of claim 7, wherein: in thehydraulically un-blocked position of the first hydraulic control system,the first three way valve is in either its extension or retractionposition, and the controller is configured such that the first hydraulicram actively facilitates the pivoting of the first swing leg.
 10. Themachine of claim 9, wherein: the controller is further configured suchthat the controller determines a degree of active facilitation of thepivoting in accordance with an algorithm.
 11. The machine of claim 9,wherein: the first hydraulic control system further includes a supplyline and a pressure control valve located in the supply line; and thecontroller is further configured such that the active facilitation ofthe pivoting of the first swing leg by the first hydraulic ram islimited to providing a hydraulic pressure to the first hydraulic ramcontrolled by the pressure control valve.
 12. The machine of claim 4,the first hydraulic control system includes: a first hydraulic ramhaving a piston and a cylinder, the piston dividing the cylinder intofirst and second ends; first and second hydraulic lines connecting afluid reservoir to the first and second ends of the cylinder,respectively; and: first and second bypass valves connected to the firstand second hydraulic lines, respectively, each bypass valve including ablocked position and a bypass position, the bypass positioncommunicating the respective end of the first hydraulic ram to the fluidreservoir; and wherein in the hydraulically blocked position of thefirst hydraulic control system the first and second bypass valves are intheir blocked positions; and wherein in the hydraulically un-blockedposition of the first hydraulic control system the first and secondbypass valves are in their bypass positions.
 13. The machine of claim 1,wherein: the first and second swing legs are forward extending swinglegs.
 14. The machine of claim 12, further comprising: third and fourthrearward extending swing legs and third and fourth ground engaging unitsconnected to the third and fourth rearward extending swing legs,respectively.
 15. The machine of claim 1, wherein: the controller isconfigured such that the swing leg pivot mode includes a manual sub-modepermitting the ground engaging units to be steered under manual controlby a machine operator.
 16. The machine of claim 1, wherein: thecontroller is configured such that the swing leg pivot mode includes anautomatic sub-mode in which the steering is automatically controlled bythe controller in response to an operator input corresponding to adesired swing leg position.
 17. The machine of claim 16, wherein: in theautomatic sub-mode the controller causes the ground engaging unit of aswing leg that is to be pivoted to be steered in an S-curve along theground surface beginning parallel to an initial direction of the groundengaging unit of the swing leg that is to be pivoted, then steering awayfrom and then back toward the initial direction.
 18. The machine ofclaim 17, wherein: in the automatic sub-mode the controller causes theground engaging unit of the swing leg that is to be pivoted to besteered back to a final direction parallel to the initial direction. 19.The machine of claim 17, wherein: in the automatic sub-mode thecontroller causes the ground engaging unit of the swing leg that is tobe pivoted to be steered back to a final direction corresponding to acurrent direction of the machine. 20-50. (canceled)